Clustered NFS server reply ERR 24: Auth Bogus Credentials (seal broken)

I have 4 servers on the VirtualBox. Two of the servers are a CentOS 7 cluster with Pacemaker(corosync), and they have an NFSv4 server in Active/Passive mode. There are also 2 clients with CentOS 6, also using this NFS server. The problem does not always occur, but sometimes when I manually or automatically failover from the active NFS server cluster, both clients give the error: *Permission denied.* The tcpdump from the clients shows: [17:24:29.271467] IP client.example.net.34236755563 > server.example.net.nfs 112 getattr [|nfs] [17:24:29.271619] IP server.example.net.nfs > client.example.net.3423675563: reply ERR 24: Auth Bogus Credentials (seal broken) Until this problem is solved nothing is working: I have tried to transfer to NFSv3, tried different cluster configurations, tried a grace period for NFSv4 from 10 to 90 seconds, with no luck. Cluster configuration: node 1: storage1 node 2: storage2 primitive p_drbd_nfs ocf:linbit:drbd \ params drbd_resource=cgp \ op monitor interval=31s role=Master \ op monitor interval=29s role=Slave \ op start interval=0 timeout=240s \ op stop interval=0 timeout=120s primitive p_fs_home Filesystem \ params device="/dev/drbd0" directory="/mnt" fstype=xfs options="noatime,nobarrier" \ op monitor interval=10s \ meta is-managed=true primitive p_ip_nfs IPaddr2 \ params ip=192.168.56.100 cidr_netmask=24 \ op monitor interval=30s \ meta is-managed=true primitive p_nfs_exports exportfs \ params fsid=0 directory="/mnt" options="rw,async,no_wdelay,mountpoint,insecure,no_subtree_check,no_root_squash" clientspec="192.168.56.0/255.255.255.0" wait_for_leasetime_on_stop=true rmtab_backup=none \ op monitor interval=10s \ op stop interval=0 timeout=120s \ meta is-managed=true primitive p_nfsserver nfsserver \ params grace_time=90 proc_num=16 \ op monitor interval=30s \ meta is-managed=true primitive p_ping ocf:pacemaker:ping \ params host_list=192.168.56.1 multiplier=1000 attempts=1 timeout=3 name=p_ping \ op monitor interval=5 timeout=60 ms ms_drbd_nfs p_drbd_nfs \ meta master-max=1 master-node-max=1 clone-max=2 clone-node-max=1 notify=true is-managed=true clone cl_p_ping p_ping \ meta is-managed=true target-role=Started location l_0 ms_drbd_nfs \ rule $role=Master -inf: not_defined p_ping or p_ping lte 0 colocation c_1 inf: p_fs_home ms_drbd_nfs:Master colocation c_2 inf: p_nfsserver p_fs_home colocation c_3 inf: p_nfs_exports p_nfsserver colocation c_4 inf: p_ip_nfs p_nfs_exports order o_1 inf: ms_drbd_nfs:promote p_fs_home:start order o_2 inf: p_fs_home p_nfsserver order o_3 inf: p_nfsserver p_nfs_exports order o_4 inf: p_nfs_exports p_ip_nfs property cib-bootstrap-options: \ dc-version=1.1.10-32.el7_0.1-368c726 \ cluster-infrastructure=corosync \ stonith-enabled=false \ no-quorum-policy=ignore \ last-lrm-refresh=1428329105 rsc_defaults rsc-options: \ resource-stickiness=200 Here is a string from the client fstab file: 192.168.56.100:/ /mnt nfs nfsvers=4,proto=tcp,rsize=32768,wsize=32768,hard,timeo=300,retrans=2,bg,actimeo=3,noatime,nodiratime 0 0